Electric circuit interrupter



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Patented Sept. 29, 193,6

ELECTRIC CIRCUIT INTERRUPTER Josef Biermanns, Berlin-Johannisthal, Germany,

assignor to General Electric Company, a corporation of New York Application December 5, 1935, Serial No. 53,074 In Germany December 15, 1934 3 Claims.

My invention relates Vto electric circuit interrupters, more particularly to those of the fluidblast type wherein the arc drawn upon opening of the circuit is subjected to an extinguishing jet or blast of huid, and has for its principal object the provision of an improved circuit interrupter of the aforesaid type which shall be uniformly effective over a comparatively wide interrupting range.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, the. single figure thereof is an elevational view, partly in section, of an electric circuit interrupter comprising my invention in the closed circuit position.

'I'he electric circuit interrupter illustrated, by way of example, comprises a base structure I on which are mounted the relatively movable contacts, comprising in the present instance a xed socket-type contact 2 of well-known construction and a coacting movable rod contact 3. The contacts which are shown in the closed circuit position engage by reason of a garter spring 4 which presses a plurality of segmental contacts into engagement with the rod contact 3.

The fixed contact 2 is mounted within a casing 5 defining a pressure-confining arc chamber, the casing 5 in the present instance being of conducting material and serving as one terminal of the circuit interrupter. The fixed contact 2 is resiliently mounted within the casing 5 by means of the spring 6.

The casing 5 is provided with an exhaust passage comprising, in the present instance, a comparatively long tubular member 'l of insulating material suitably secured to the casing 5. The rod contact 3 is guided within the tube 'I and forms a fairly close fit with the tube so that exhaust from the arc chamber is to a great extent precluded as long as the rod contact 3 is in the exhaust passage.

.The operating means for the rod contact comprises an insulator 8 pivotally mounted at 9 on the base and connected at its upper bifurcated end I to a forked member I 0, which is in turn connected at II to an extension I2 of the rod contact. The extension I2 is slidably guided at I 3 in the other terminal structure I3. Accordingly, an operating force suitably applied to the shaft .9 for rocking the insulator l is effective to move the rod contact 3 into or out of engagement with the coacting fixed contact 2, the contact 3 in the open (Cl. 20G-148) circuit'position being exteriorly of the tube l so that arcing pressure within the casing 5 is suddenly released to cause a fluid blast through the arc between the contacts 2 and 3. The terminal casing 5 and the terminal structure at I3 are each suitably supported on the base I by insulators I4 and I5, respectively.

In the arrangement so far described, wherein the chamber in which the fixed contact is disposed is filled with air and merges into an insulatl0 ing tube closely surrounding the contact rod, the arc created upon opening of the circuit forms a more or less high pressure, either by heatingithe air in the arc chamber or by the evaporation of the insulating material with which the arc comes in contact. The amount of the pressure created is of considerable importance for proper interruption of the arc. In order, therefore, to interrupt comparatively low currents with certainty, it has been proposed to us a comparatively small switch rod operating within as restricted a space as possible. Adequate pressure at comparatively low currents may in such a case be generated. However, in this case the arrangement could not be used for high currents which require a switch rod of much larger diameter, since, if the diameter of the rod is increased, the interruption of the arc at low currents will not be satisfactory or uniform by reason of the increased volume of the arcing space.

In accordance with my invention, the circuit interrupter is provided with a source of auxiliary fluid pressure which is effective at low currents for augmenting or supplanting the arc pressure in the arc chamber and which at high currents i is connected at I 6 through a piston rod Il to a piston I8, the piston operating within a cylinder I9 which is arranged to be in communication, 50 through the conduit 2li, with the arc chamber in thecasing 5. A valve 2| is disposed in the casing 5 for controllingsthe passage through the conduit 20 and is biased by a light spring 22 into seating engagement so as normally to close said passage,

the valve being seated so as to be opened by pressure within the conduit 2li.

Accordingly, at low currents the compressed gas supplied by the piston i8 increases the pressure within the arc chamber so that the arc is effectively interrupted when the rod l leaves the tube 1, whereas at high currents the arc itself produces sumciently large pressure for interrupting the circuit. In the case of lo currents, the valve 2| admits, without appreciable resistance, gas under pressure to the arc chamber and at some predetermined higher current the arcing pressure within the chamber is greater than the pressure developed by the piston I8, with the result that the-valve 2| is closed and the exhaust from the arcing chamber is confined to the insulating tube 1. The valve 2l, therefore,`not only serves to maintain proper blast pressure within the arc,

chamber at higher currents, but also prevents the arcing pressure from acting on the piston I8 and momentarily reclosing the switch. g

It should be understood that my invention is not limited to speciilc details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An electric circuit interrupter of the fluidblast type comprising 'relatively movable contacts, one of said contacts being disposed within a pressure-confiningv arc chamber and another of said contacts being movable from said chamber, arc pressure generated in said chamber causing a fluid blast in the direction of said movable contact, an auxiliary source of fluid pressure arranged to be in communication with said chamber, and a valve between said chamber and source arranged to close when the arc pressure in said interrupting chamber exceeds that of said source.

2. An electric circuit interrupter of the uidblast type comprising relatively movable contacts, one of said contacts being disposed within a pressure-connng arc chamber, said chamber having an exhaust passage defined by a comparatively long tubular member of insulating material, another of said contacts comprising a movable rod for engaging the aforesaid contact in said chamber, said rod being closely surrounded by said insulating tube and movable to an open circuit position exteriorly of said tube, an auxiliary source of uid pressure arranged to be in communication with said chamber for supplying pressure to said chamber at low currents, and a valve disposed in said chamber controlling communication between said chamber and source arranged to close when the arc pressure in said chamber exceeds the pressure of said source.

3. An electric circuit interrupter of the duldblast type comprising relatively movable contacts, one of said contacts being disposed within'a pressure-confining arc chamber, said chamber having an exhaust passage defined by an insulating tube, another of said contacts comprising a movable rod slidable through said tube for engaging the aforesaid contact in said chamber, said rod hav-` ing a. comparatively close flt in said tube and movable to an open circuit position exteriorly thereof, a source of pressure arranged to communicate with said chamber including a piston operatively connected to said movable rod contact, said piston supplying auxiliary pressure to saidchamber at low currents, and a valve positioned between said chamber and piston arranged to close when the arc pressure in said chamber ex'`v ceeds the pressure produced by said piston.

JOSEF BIERMANNS. 

